Gating trigger circuit



July 14, 1953 D. H. PRlTcHARD GATING TRIGGER CIRCUIT Filed om. 27. 1956,

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Patented July 14, v1953 GATING TRIGGER CIRCUIT Dalton H. Pritchard, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application'October` 27, 1950, Serial No. 192,470

This invention relates to trigger circuits and more particularly to trigger circuits used as electronic switching devices.

Electronic switches are known in the art wherein a free-running multivibrator, which can be synchronized with an external signal, has its output applied to a pair of electronic gates to open them alternately to permit passage of signals which are applied to the gates; Where ran- `dom alternate switching` is desired a bistable state type of trigger circuit is used in placeof` the free running multivibrator. Such switches require a minimum of four electron discharge devices, two for switching signals and two for gating. A more economical and simpler electronic` switchcould be constructed if it were possible to eliminate `the electronic gates and have the multivibrator or 'trigger `circuit itself perform both the gating and amplication functions performed by presently known electronic switches.

In apatent to James R. Weiner, No. 2,502,687, for Multivibrator and Control of Same there is. described a free-running multivibrator circuit which performs both the gating and amplication functions. Signals'to be g-ated and amplified are applied to the cathodes of the two tubes comprising the multivibrator and signals to synchronize the gating action are applied to the. control grids of the multivibrator. In order to obtain such operation Weiner provides diodes which serve as a Icharging path for the multivie brator cross-coupled condensers other than the Other diodes serve to blockA the chargingpaths through the grid-to-cathode impedances. This provides a multivibrator in which each section may operate as a class A amplier because the control grids can operate at a negative potential. It shouldbe noted that besides requiring diodes as extra circuit elements the device of Weiner is a free-running one which is synchronized, not controlled by the externally applied synchronizing pulses.` The devicevdoes not permit random keyingof two signal channels. Such keying is a desirable feature ,in many applications. lOne such is the diversity combining action required rin a dual diversity receiving system which is random in nature.

It is thereforeran object of my present invention to provide a novel and improved combined tion to provide a simple and inexpensive combined gating and trigger circuit which permits random operation.

These and other objects of my present invention` are achieved by using a `trigger circuit of the D. C. coupled, cross-connected Eccles-Jordan type which has two stable conditions. The tubes used inthe trigger circuit are pentodes and the triggering action is obtained by cross-connecting the anode and suppressor grids of the tubes. The anode, suppressor grids and control grids of each tube are connected to various .points oi two voltage dividers which are across a source of operating potential. The values of the resistors of the voltage divider are `such that potentials are applied to the suppressor grids and anodes to maintain the trigger circuit stable with conduction in either one of the two tubes. Further, a Class A operating bias is applied to the control grids in the one of the two tubes which ismade conducting to permit itto operate as an amplier. Switching signals are applied to the suppressor grids and the signals to be keyedand amplified are applied to the control grids. v

The novel features of the invention as well as the invention itself both as to its organization and method of operation will best be understood from the following description when read in connection with the accompanying drawing, which shows a circuit diagram of an embodiment of the invention. 1 l

In `the drawing there may be seen a gating trigger circuit consisting of a rst electron' discharge tube Ill and a second electron discharge tube I2. Each has an anode load `resistor 34, 3B, connecting its anode I4, 24 to a source of B+ or operatingpotential. The anode I4 of the first tubeV I0; is connected tothe suppressor grid 26 of the Vsecond tube I2 through a coupling resistor 38; The anode 24 of the second tube I2 is i connected to the suppressor grid I6 of the rst tube` Iii` through a coupling resistor 4I).` The screengrids I 8, 28 of both tubes are connected together and to the source of B+ through a single resistorl 42. They are alsobypassed to ground through ajcondenser'llll. "lfworesistors 46, 48 connected in` series connect the first tube supv presser grid I 6 to a negative` bias source or B-.

rThe control grid 28 of the first tube Il) is connected, through a grid'lead Yresistor 54, to the Ajunction of the two series connected resistors 46,

48; Another two series-connected resistors 50, 52- connectV the suppressorgrid 26 of the second tube I2 to the negative bias source. Thecontrol grid 30 of the second` tube is connected The cathodes 22, 32 of both tubes are con-A the suppressor grid of a pentode tube as a control element. Operation of the Eccles-Jordan trigger circuit using a suppressor grid as the control element may be found fully described on pages 54-56 of a book published by John Wileyh and Sons, Inc., called Time Bases, by O. S. Puckle.

The Circuit shown in the drawingf'dis-VV tinguishes over the conventional Eccles-Jordanl type of trigger circuit in the typesof bias applied-1v to the screen grids and-to the control grids by reason of the values selected for the two voltage dividers formed by the anode resistors 34, 36 coupling resistors 38, 4B and two series-connected resistors'llG, 48 and 553, 52, and the unique dispositiony of such Voltage dividers for the Aobtention of such bias permitting hitherto totally kunexpected and useful additional uses to be obtained from the trigger circuit.

- vrThe circuit shown, by reason of its connections and the values chosen for its components, has two stable operating conditions.v One condition results in the first tube Il) at cut-oil and the second tube l2 conducting. The application of aA negative pulsel to the second tube suppressor grid 26 serves to trigger the circuit so that the second tube is cut off, applying a relatively positive potential from its anode 24 to the first tube suppressor grid I6, causing this tube to conduct and to apply a relatively negative potential to the second tube'suppressor grid 26. Application of a negative pulse to the rst tube suppressor grid I6 restores conduction to the second tube again and cut oil conduction in the iirst tube.

For an explanation of the operation of the gating trigger circuit, assume that the circuit is stable with the second tube conducting and the first tube essentially cut 01T. The anode potential of the rst tube is then close to B+. The

`values of the Voltage divider components are selected to be such, however, that the suppressor grid 26 of the second tube l2 is left at ground or l cathode potential, this being its normal operat- B are amplied and may be derived from the second tube anode 24. By a Class A operating Y bias is meant a negative bias which permits the tube to have anode current owing at all times. The rst tube l, by reason of the negative potential applied to its suppressor grid I6 is at cut 01T and no signals will be passed through it from signal sourceA coupled tol its control grid 20.

If a negative pulse is applied to the suppressor grid of the second tube sumcient to cut it 01T and cause vthe rsttube to become conductive, then,

by reason of the values selected for the Voltage Vdivider bias source, the suppressor grid Hi of the rst tube is placed at cathode potential, a Class A` operating bias is placed on the control grid 2E] of the rsttube and it then serves asvan amplifier for llonger passed through the second tube.

the signals from the signal source A connected to its grid. Signals from signal source B are no Thus, the gating trigger circuit serves to gate and amplify the signals from sources A and B at random or in accordance with the frequency of the triggering signals from the control source 58. Needless lto say, the signals' from the signal sources A and B should not be f an amplitude suilicent to drive the tube to which they are applied to cut oil, since this will have the effect of transferring tube conduction. The circuit may also be used to gate one signalV as desired with no additional circuitry. The source of operating potential may be a single source of potential which ranges in Value above and below the reference potential point or ground potential.

From the foregoing description it will be readily apparent that I have provided an improved gating trigger circuit that is simple and economical and permits a random gating of signals. Although a single embodiment of my present invention has been shown and described, it will vbe apparent that changes may be made vinthe particular embodiment herein disclosed, and

that other embodiments are possible, al1 within the spirit and scope of the invention. Therefore, it is desired that the foregoing description shall be taken as illustrative and not as limiting;

What is claimed is:

l. A system for random alternate amplication of signals from two signal sources comprising a;

trigger Acircuit including a first and a second electron discharge tube each having an anode, a cathode, a control grid and a suppressor grid, a lirst and a second three-tap voltage divider, means to apply an operating potential across said rst and second voltage dividers, said rst and second tube anodes being respectively connected to a rst tap on said rst and second three-tap voltage dividers, said irst and second tube suppressor grids being respectively connected to a second tap on said second and .rst three-tap voltage divider, said first and second tube control grids being respectively coupled to a third tap Von said second and rst Ythree-tap voltage dividers, means establishing a point of reference potential, the cathodes of said first and second tubes being connected to said point of reference potential, the values of impedances of said rst and second voltage dividers being determined to provide potentials at said rst and second taps to maintain said rst and second tubes stable with conduction in either one of said tubes and to provide a potential at said third taps such that a Class A -bias is applied to the control grid in a conducting one of said lirst and second tubes, means coupling each of said two signal sources to each of said control grids and means to apply trigger control signals to said suppressor grids to transfer conduction between said iirst and second tubes. l

2. A gating trigger circuit comprising a pair of electron discharge tubes each having an anode `a cathode, a control grid, and a suppressor grid, means coupling the suppressor grid of one of said tubes to the anode of the other of said tubes andV 3. 'A system for random alternate ampliiication of signals from two signal-sources comprising a rst and a second electron discharge tube ea'ch having an anode, a cathode, a control grid, a screen grid and a suppressor grid, a pair of anode, load resistors each connected to one of said tube anodes, a pair yof coupling resistors, one of which is connected between said first tube anode and said second tube suppressor grid, the other of which is connected between said second tube anode and said rst tube suppressor grid, a pair of two series connected resistors, each of said pair having one end connected to one of said suppressor grids and the other end connected together, a first resistor Coupling said rst tube control gridwith the junction between the two series connected resistors which is the one of said pair which is connected to said first tube screenl grid, a second resistor coupling said second tube control grid with the junction between the two series connected resistors which is the other one of said pair, means establishing a point of reference potential to which the cathodes of said 6v first and second tubes are connected, means to apply an operating potential having values above and below said point of reference potential to said anode load resistors and the connected together end `or said pair of two series connected resistors, said pair of anode load resistors, pair of coupling resistors and pair of two series-connected resistors having values determined to provide potentials to maintain said iirst and second tubes stable with conduction in either tube and to apply a substantially reference potential to the suppressor grid in a conducting one of said first and second tubes and to apply a class A bias to the control grid in the conducting one of said rst and second tubes, means to apply signals from each of said two signal sources to each of said controi grids, means to derive an output from each of said anodes, and means to apply trigger control signals to said suppressor grids to transfer conduction between said rstand second tubes.

DALTON H. PRITCHARD.

References Cited in the :tile of this patent UNITED VSTATES PATENTS Number Name Date 2,448,336 Weiner Aug. 31, 1948 2,534,232 Cleeton Dec. 19, 1950 OTHER REFERENCES Time Bases by Puckle, December 19, 1947; pages 54 to 5'7. 

